1. Field of Invention
The present invention generally relates to an inkjet printhead chip structure and a manufacturing method for the same and, particularly to a thermal inkjet printhead chip structure that can buffer against a transient high temperature generated by a resistive layer thereof and a manufacturing method for the same.
2. Description of the Related Art
Various kinds of thermal inkjet printhead chip structures have been developed. For example, a thermal inkjet printhead chip structure as disclosed by U.S. Pat. No. 5,122,812 (the disclosure of which is incorporated herein by reference) includes a driver circuitry formed on a substrate and an insulating oxide layer, and a resistive layer formed on the substrate and directly electrically connected to a source and a drain of the driver circuitry. A conductive metal layer then is formed on the portions of the resistive layer. The area of the resistive layer that is not covered by the conductive layer functions as a heating area. The heating area of the thermal inkjet printhead chip structure would instantly generate an extremely high temperature when the driver circuitry is in operation, which would result in the substrate and the insulating oxide layer underneath the heating area becoming cracked. Such a phenomenon is termed as thermal shock and would shorten the life span of the thermal inkjet printhead chip structure.
U.S. Pat. No. 5,710,070 and U.S. Pat. No. 5,870,121 both disclose another type of thermal inkjet printhead chip structure, the disclosures of which are incorporated herein by references. Specifically, a resistive layer is formed on a dielectric layer. The resistive layer is comprised of two layers. The first layer of the resistive layer is made of metal and acts as a barrier between the dielectric layer underneath the first layer and the second layer and further can improve the electrical conductivity. Since the first layer acting as the barrier is made of metal with excellent thermal conductivity, the thermal shock suffered by the dielectric layer still does not be relieved, so that the life span of the thermal inkjet printhead chip structures is shortened.
U.S. Pat. No. 5,774,148 discloses still another type of thermal inkjet printhead chip structure, the disclosure of which is incorporated herein by reference. In particular, a boron-phosphorus doped silicate glass (BPSG) material is formed between a resistive layer and a silicon dioxide layer. The BPSG material has a serious stress issue, so that the BPSG material would more easily become cracked when encountering a high temperature generated by the resistive layer in operation. Therefore, the lift span of the thermal inkjet printhead chip structure would be severely influenced.